Project Summary The multifunctional endothelial interface between blood and tissues is an important target for therapeutic interventions in many human maladies. To achieve precise interventions, many labs including us conjugate drugs and drug carriers with affinity ligands that target cargoes to the endothelium. On the other hand, carriers that accumulate in tissues via non-affinity mechanisms may provide an additional boost in drug delivery capacity. We have found that reversible association of nanocarriers (NCs) with the red blood cell (RBC) surface provides a new strategy combining targeted and non-targeted approaches. NCs adsorbed onto isolated RBCs (RBC/NC) rapidly transfer to the vasculature downstream of the injection site and avoid hepatic uptake. Pilot data show that we can synergize the power of RBC-hitchhiking and affinity targeting. Loading on RBCs provides almost three orders of magnitude boost of uptake of EC-targeted NCs in the lungs. Further, RBC-targeted NCs safely load onto RBCs in vivo, which allows us to avoid transfusion. To combine these advantages and enable transfer from RBCs to ECs, we have designed dual-targeted NCs (DTNCs) by conjugating to opposite facets of anisotropic ?Janus? particles ligands that bind to RBCs and EC. Fine-tuning of each facet's avidity maximizes spatiotemporal control of targeting to RBCs and transfer to ECs. We identified ligands selectively targeting NCs to the brain vs lungs. The goal of this proposal is to define the mechanism and enable translation of this novel, paradigm-shifting strategy. We will employ mutually reinforcing models: in vitro (microfluidic), ex vivo (perfused human lungs) and in vivo (nave vs pathological animals). We will study NC loading onto RBC and the transfer to and localization in recipient cells, and the effect of drug delivery by RBC-hitchhiking in three independent Aims. Aim 1: Loading NC onto RBCs. We will: A) Define optimal NC design for RBC loading; B) Engineer RBC-targeted NC loading in vivo; and, C) Determine the biocompatibility of NC-loaded RBCs. Aim 2: NC unloading and transfer. We will characterize and optimize vascular transfer of untargeted NCs vs EC-targeted and dual-targeted NCs: A) Kinetics and amplitude of transfer; B) Cellular addressing and trafficking of NCs; and, C) Pathophysiological factors modulating transfer. Aim 3: Translational RBC hitchhiking. We will: A) Appraise beneficial vs unintended effects of delivery of anti-inflammatory agents by RBC/NC; B) Refine NC targeting to human RBC; and, C) Recapitulate key findings of animal studies in perfused human lungs. This study will advance: A) Design of drug delivery systems combining targeted nanocarriers with ?supercarrier? RBCs; B) Understanding of important vascular interfaces; C) Development of precisely targeted pharmacotherapy for treatment of ALI/ARDS and likely stroke and other common acute crises.